In recent years, rapid advances have been made in digitalization of information. This has led to remarkable efforts to meet with this in the imaging field.
In particular, as symbolized by the digital camera, in imaging surfaces, the conventional film is being taken over by use of solid-state imaging elements such as CCDs (charge coupled devices) or CMOS (complementary metal oxide semiconductor) sensors in most cases.
An imaging lens device using a CCD or CMOS sensor for the imaging element in this way optically captures the image of an object by the optical system and extracts the image as an electric signal by the imaging element. Other than a digital still camera, this is used in a video camera, a digital video unit, a personal computer, a mobile phone, a personal digital assistant (PDA), an image inspection system, an industrial camera for automatic control, and so on.
FIG. 1 is a view schematically showing the configuration of a general imaging lens device and a state of light beams.
This imaging lens device 1 has an optical system 2 and a CCD or CMOS sensor or other imaging element 3.
The optical system includes object side lenses 21 and 22, a stop 23, and an imaging lens 24 sequentially arranged from the object side (OBJS) toward the imaging element 3 side.
In the imaging lens device 1, as shown in FIG. 1, the best focus surface is made to match with the imaging element surface.
FIG. 2A to FIG. 2C show spot images on a light receiving surface of the imaging element 3 of the imaging 20, lens device 1.
Further, imaging devices using phase plates to regularly disperse the light beams, using digital processing to restore the image, and thereby enabling capture of an image having a deep depth of field and so on have been proposed (see for example Non-patent Documents 1 and 2 and Patent Documents 1 to 5).
Further, an automatic exposure control system of a digital camera performing filter processing using a transmission function has been proposed (see for example Patent Document 6).
Further, in a CCD, CMOS, or other device having an image input function, reading a barcode or other proximate still image together with for example scenery or another desired image is extremely useful in many cases.
A barcode is read for example narrowing an F value in for example a camera so as to expand the depth of field and obtain a fixed focus by the technique of focusing by auto-focusing extending a lens as a first example or a depth expansion technique as a second example.
Further, a technique of increasing the field in focus is disclosed in for example Patent Document 8.
Non-patent Document 1: “Wavefront Coding; jointly optimized optical and digital imaging systems”, Edward R. Dowski, Jr., Robert H. Cormack, Scott D. Sarama.
Non-patent Document 2: “Wavefront Coding; A modern method of achieving high performance and/or low cost imaging systems”, Edward R. Dowski, Jr., Gregory E. Johnson.
Patent Document 1: U.S. Pat. No. 6,021,005
Patent Document 2: U.S. Pat. No. 6,642,504
Patent Document 3: U.S. Pat. No. 6,525,302
Patent Document 4: U.S. Pat. No. 6,069,738
Patent Document 5: Japanese Patent Publication (A) No. 2003-235794
Patent Document 6: Japanese Patent Publication (B) No. 2004-153497
Patent Document 7: Japanese Patent Publication (C) No. 2004-37733
Patent Document 8: Japanese Patent Publication (D) No. 2002-27047